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One of the impacts of climate change is extreme weather events that often bring heavy rainfall and flooding to some areas. Heavy rainfall increases organic runoff into freshwater and coastal waters, and according to a study that was recently published in Scientific Reports, may inhibit the sun's ability to penetrate these waterbodies. As UV light is able to kill pathogens, the sun's ultraviolet (UV) rays provide important ecosystem services, ridding rivers, lakes and coastal waters of pathogens. If this ability is diminished, there is a greater likelihood of waterborne pathogens becoming more prolific.

Research has shown that globally aquatic systems are becoming browner due to the increase in organic material being washed into them from surrounding terrestrial systems — a phenomenon known as "browning". Using a model developed by the National Center for Atmospheric Research (NCAR), this latest study is the first to quantify the impact that dissolved organic material has on limiting the sun's UV rays from disinfecting waterbodies and killing pathogens that lurk in them.

This not only poses a potential health risk for people who are exposed to pathogens when using waterbodies for recreation, but also poses a potential drinking water safety risk — even if the water has been treated. According to Craig Williamson, an ecologist at Miami University and lead author of the paper, dissolved organic matter doesn't only inhibit the ability of the sun to disinfect water, it also renders the water treatment process less effective. Considering that every year between 12-19 million people already fall ill in the US alone due to exposure to waterborne pathogens, this will in all likelihood cause that figure to rise.

For the study, the researchers analyzed water samples collected from lakes in the US and other countries to determine the level of dissolved organic matter present in each of the samples and the wavelengths of ultraviolet light absorbed by the organic matter present.

Then using the Tropospheric Ultraviolet-Visible model — which simulates how UV light is scattered and absorbed as it passes through Earth's atmosphere — the scientists estimated how much of the sun's UV rays reaches the surface of these lakes at different times of the year. They also assessed the amount of reflection and refraction of light from the surface of each lake to determine how much UV light penetrates together with the depth it reaches.

According to the report, "the Tropospheric Ultraviolet-Visible model also calculates the expected disinfecting power of UV light in a particular body of water based on its dissolved organic matter and other characteristics, a measurement known as 'solar inactivation potential (SIP)'. In some cases, researchers calculated the SIP across different parts of, or for different time periods in, the same lake."

From there the researchers were able to quantify the impact that dissolved organic matter had on water quality of lakes, as well as drinking water supplies. For example, modeling of water samples collected prior to and following a severe storm from a site on Lake Michigan — a source of drinking water for over 10 million consumers — showed a 22% reduction in SIP due to the additional dissolved organic matter that flowed into the waterbody from just this one storm.

"Water clarity is dropping in many regions due to factors such as browning, and this research demonstrates that this change is likely decreasing natural disinfection of potentially harmful pathogens," said Kevin Rose, a freshwater ecologist at Rensselaer Polytechnic Institute and coauthor of the paper.

Water contamination by microbial contaminants is a widespread problem throughout the country. These contaminants make their way into freshwater systems, where they pose a health to humans. While water regulators routinely test water sources for these types of contaminants, the methods used are outdated and unreliable.

Now, researchers from the Lawrence Berkeley National Laboratory (Berkeley Lab) have found a way to not only accurately detect microbial contaminants in our waterways, but also to distinguish between different sources of those contaminants.

Using an award-winning device known as a PhyloChip, which is about the size of a credit card, and which can reliably detect more than 60,000 microbe species, water regulators can now test the waters with greater accuracy. During preliminary testing of the device on Northern California's Russian River watershed, the scientists found cases where this new identified microbes that posed a potential health risk to humans that had not been detected by conventional fecal count tests. The study, which was recently published in the scientific journal Water Science, also found that in some cases the conventional testing methods flagged bacteria that were not considered a health risk to humans.

"With the PhyloChip, in an overnight test we can get a full picture of the microorganisms in any given sample," said Eric Dubinsky, a microbial ecologist at Berkeley Lab and lead author of the paper. "Instead of targeting one organism, we're essentially getting a fingerprint of the microbial community of potential sources in that sample. So it gives us a more comprehensive picture of what's going on. It's a novel way of going about source tracking."

Local water regulators currently collect water samples, and then culture the bacteria for 12 hours before checking the levels of two key bacteria types: Enterococcus and E. Coli — which are considered indicators of fecal contamination. But this method fails to distinguish between different sources of the bacteria, which could have originated from cattle, waterfowl, humans, sewage or even rotting vegetation.

"These tests have been used for decades and are relatively primitive," Dubinsky said. "Back in the 1970s when the Clean Water Act was developed and we had sewage basically flowing into our waters, these tests worked really well. Epidemiological studies showed an association of these bacteria with levels of illness of people who used the water. These bacteria don't necessarily get you sick, but they're found in sewage and fecal matter. That's why they're measured."

While it is easy to identify point sources, such as sewage outfalls, which generally get cleaned up once they have been identified, non-point sources of pollution, such as runoff from agricultural lands, are more difficult to identify, and are becoming a growing concern.

The PhyloChip, which was developed by co-author, Gary Andersen, a microbial ecologist at Berkeley Lab, together several colleagues at Berkeley Lab, has proven useful for a number agricultural, medical, and environmental applications, including gaining a better understanding of coral reef ecology, air pollution, and environmental conditions in the Gulf of Mexico following the BP oil disaster. The PhyloChip has 1 million probes which enable it to identify microbes according to variations in a specific gene, without the need to culture the bacteria overnight. The scientists soon realized that the PhyloChip held great potential for assessing water quality and pinpointing the source of water contaminants.

It is no simple task to determine the source of a pathogen. In many cases, more than one type of microbe is needed to determine the source, as the microbial community of animals such as cows can consist of a thousand different microbial organisms.

To address this, the scientists coerced a lab intern into going around and collecting poop from a wide range of animals. They then set about cataloguing the microbial communities found in the poop specimens of cattle, horses, pigs, raccoons, sea lions, different bird species, as well as other wildlife, humans and sewage, using that catalogue to develop a model which compares an unknown microbial sample with the samples in their reference library.

"We've used the PhyloChip in a way that it hasn't been used before by using machine learning models to analyze the data in order to detect and classify sources," Andersen said. "It's essentially giving you a statistical probability that a microbial community came from a particular source."

After comparing their method with forty others used to track sources of microbial contaminants, their method proved to be the only one that could reliably detect all microbial sources correctly. Even when the microbes originate from an animals source that is not listed in their library catalogue, this method can still prove to be extremely useful in identifying the source. For example, in one study the sample was from a chicken, but the team had not yet analyzed chickens. However, they did have records of pigeons, gulls and geese, which enabled them to determine that the sample came from a bird.

After extensive sampling within the Russian River watershed, which currently does not comply with the Clean Water Act, the scientists discovered that contamination from human sources was widespread around areas where communities depend largely on aging septic tank systems. They also detected significant contamination from human sources following a weekend jazz concert, which was not as clearly evident when using the other methods. Dubinsky attributes this to the fact that this new methods is much more sensitive to human contaminants that the outdated fecal indicator tests.

The Berkeley Lab scientists are currently working together with the EPA to develop the method further so that it can be used universally at any location, by anyone, even non-experts. The method also holds promise for determining the sources of nutrients that fuel algal blooms, particularly in the Great Lakes, where this continues to be an ongoing problem.

If you're concerned your water may be contaminated, the Berkey systems equipped with the black berkey filters will remove bacteria and viruses to levels greater than 99.9999%